1. The Field of the Invention
The invention of our prior application, now U.S. Pat. No. 5,109,847, generally relates to an apparatus that modulates the neurological responses associated with certain biological dysfunctions, neural pain, and pain caused by blood flow deficiency. More specifically, it is an apparatus and system for the treatment of selected pain and/or neural dysfunction-induced maladies.
The present relates to improvements thereof; more specifically, an apparatus for the topical iontophoretic administration of medication for the treatment of various conditions, and an apparatus for modulating neural responses using an additional modulation frequency.
2. The State of the Art
The sensation of pain is associated with numerous physiological and psychological ailments and is a universal experience of all complex living organisms. Pain, as the mental manifestation of a neurological response, is an important biological attribute and is critical to living and enabling a person to understand dangers in the environment and to adapt thereto. Concomitant with this important role, the alleviation of pain has been a fundamental goal of medicine and philosophy for as long as the medical profession has existed. Indeed, the ability to control the neurological pathways through which pain is conveyed has made complex procedures far simpler to implement and much less traumatic to the patient.
There is a class of neurological response which is associated with pain that does not correspond to or act as a warning for a particular physical damage or biological dysfunction. In fact, many biologically important transitions are characterized by significant pain, such as the withdrawal period of an addict, during which time the addict's system is depleted of a specific endogenous narcotic. Other mental conditions which are neurologically response-dependent conditions include depression, hypertension, causalgia pain, insomnia and jet lag. Analogous to pain being an indication that the local environment is being dangerous, occurrences such as jet lag and drug withdrawal are both essentially a severe change in a person's environment.
The importance of the ability to control neurological response and associated perceptions of pain and distress has led to the development of many pain control methodologies. The most common of which employs bio-active chemical agents that act to block neural transmission pathways within the body. These are designed to operate locally for spot treatment or broadly for generalized control or inhibition of pain response throughout the body. Chemical interference with pain signals has broad based appeal, but in many instances is unacceptable. For example, some chemicals have toxic side affects or cause allergic reactions to certain patients. For more chronic ailments, such as chronic migraine headache syndrome, repeated absorption of chemical narcotics may reduce the associated pain, but at unacceptably high costs associated with interference with routine activities, addiction, and/or toxicity of the narcotic.
In view of the problems associated with chemical pain control, efforts have abounded to discover treatment approaches which would not involve pharmacological (chemical) interference with neural transmitters in the body. One approach that has recently sparked tremendous interest is the use of low power electrical stimulator devices capable of passing currents across key neural transmitter junctions in the body and thus effecting a blockage of neurological pathways which are inducing messages of pain to the brain. A practical implementation of this approach is disclosed in U.S. Pat. No. 3,902,502 to Liss, et al; the teachings of which are herein incorporated by reference.
The system disclosed in the '502 patent presented a pulsed direct current waveform having a high frequency carrier modulated by a single low frequency modulation. It was discovered that this waveform was particularly successful at controlling symptoms of certain neurological disorders.
Although effective for its applied treatment, many electrical stimulatory devices are limited to certain applications and lack the requisite flexibility for broad-based appeal. In addition, a drawback to the use of electrical stimulation to control pain is the concern by patients and others about the impact of power dissipation on the patient. Although low current, the power dissipation of many of the electrical stimulation devices is still quite significant. Efforts to reduce the applied power have resulted in stimulation devices with little or no physiological impact.
There has been, therefore, a search for new electrical stimulation devices characterized by exceptional pain management capabilities while reducing the overall patient exposure to electrical energy.
It is also clear that pain can be caused by organic physiologic conditions, trauma, infections, and the like. While systemic analgesic agents have been used with some success, it is often desirable to attempt administration directly to the area of the patient where the medication is required. This concept also has application to the administration of a wide variety of pharmacological agents. For example, Joseph Kleinkort delivered a presentation almost a decade ago at the USAFE Medical Convention in Garmisch, Germany, in which he described to iontophoretic administration of hydrocortisone; the technique was referred to as transionic injection. Using two moistened electrodes and a particular type of micronized hydrocortisone dispersed in a petrolatum ointment base, it was found that transionic injection was as effective as percutaneous injection. The apparatus used by Kleinkort provided an electrical waveform to the electrodes which consisted of a carrier frequency of 12-20 KHz and a modulation frequency of 8-20 Hz.
More recently, Sibalis in U.S. Pat. No. 5,135,478, the disclosure of which is incorporated herein by reference, described an electrical transdermal drug applicator which provides a particular waveform to counteract the apparent decrease in the amount of the pharmaceutical delivered as the duty cycle of the apparatus increases (i.e., the time during which current is "on" relative to the time current is "off"). Sibalis provides a waveform to the electrodes which comprises a negative conditioning pulse and a sequence of different waveforms which dilate blood vessels, impede coagulation and vasoconstriction, and thereby allow for better transdermal delivery of the drug. The complex waveform generally uses an AC carrier frequency of 1.5-3.5 MHz, a pulse width of 1.25-11.25 ms, and is modulated by both an AC modulated :square wave at 250 Hz and a second AC modulator at 570-870 Hz.
There is yet a need for the improved transdermal delivery of drugs, including improved tissue wetting management, minimization of the amount of electrical energy delivered to the patient, improved patient response and comfort with the procedure, and there is especially a need to tailor the aspects of delivery with respect to the particular drug or combinations of drugs used.